Vapor generator



July 28, 1942.

W. F. KEENAN, JR

VAPOR GENERATOR Filed Jan. 10, 1940 3 INVENTOR i 39 '7 MLTf/P 166: 1; J2.

ATTORNEY Patented July 28, 1942.

VAPOR: GENERATOR Walter F. Keenan, J r., Pelham Manor, N. Y.; Anne B. Henderson, executrix of Walter F. Keenan, Jr., deceased, assignor to Foster Wheeler Corporation, New York, N. Y., a corporation of New York Application January 10, 1940, Serial No. 313,175

3 Claims.

This invention relates to vapor generators and more particularly pertains to a method of, and apparatus for, the recovery of heat in vapor generators. The invention will be disclosed in con- -r ecu0n with a steam generator, but it will be understood that it is not limited to this particular application, but is capable of general application to vapor generators.

The invention provides a method of, and means for, economically recovering a required amount of heat from high temperature flue gases, and for furnishing an adequate supply of water conrining no steam for steam washing purposes, by

"1e combined cooling efiect of a non-steaming monomizer feeding direct to the washer in the ,zoiler drum, .and by a natural circulation waste 21.63117 boiler section which is independently connected with said drum, but which is housed within the same casing structure as the econo- .lnizer.

Heretofore in certain steam plants operating to produce high temperature outlet fiue gases, it has frequently been found necessary to employ steaming economizers in order to recover a sufficient amount of heat from the gases before they pass to a stack or other heat recovery apparatus. However, a major problem encountered in connection with such steaming economizers is the separation of the steam and Water from the mixture thereof, before this mixture enters the steam and water drum of the boiler. The need for this separation, aside from the problem of steam washing, is primarily due to the practical limitations under high pressure operating conditions that are imposed on the diameter and Wall thickness of these drums. They should be of sufficiently ample dimensions to provide for separation of the steam and water normally liberated therein by the boiler tubes, but the size becomes excessive if they are also required to separate the steam and water received as a mixture from a steaming economizer. The use of a steam washer of adequate proportions under such conditions would ordinarily be impossible. Moreover, it is extremely doubtful that a mixture of steam and Water could be effectively used to Wash steam.

However there have been numerous instances, particularly in connection with modern high pressure steam boiler plants, where various factors entering into the design and operation of such units, have made the joint use of both steaming economizers and steam washers highly desirable. The steam washers are required on account of the high concentration of solids occurring in boiler circulating water which if not removed, would afiect thequality of the superheated steam with respect to turbine operation.

The economizers have been considered essential because of the high temperature (12001400 F.) of the flue gases, and the relatively large proportion of this heat which heretofore ordinarily could most economically be recovered by a steaming economizer For example, in many such installations the maximum heat recovery possible by air heating surface is limited by the maximum air temperatures permissible with existing fuel burning equipment, While stage bleeding of turbines has reduced the heat recovery possible in non-steaming economizers by increasing feed water temperatures to levels regularly above 400 F. and at times as high as 500 F. at the economizer inlet. Ordinarily therefore, since furnace gas temperatures are substantially fixed by the desired final steam temperatures, there would be a margin of several hundred degrees that would have to be absorbed by additional boiler heating surface in front of the economizer, or by a steaming economizer. However, in most cases, the installation of more ordinary boiler surface is very difficult, due to drum limitations, and in all instances exceedingly expensive when based on the amount of heat recovery thus obtainable, Whereas the use of additional economizer heating surface although much cheaper and more effective from the standpoint of heat recovery, necessitates special means for the separation of the steam and water from the mixture of the same, which is of primary importance when steam Washers are used.

The. present invention provides means and a method of overcoming these disadvantages. The invention will be understood from the following description when considered in connection with the accompanying drawing forming a part thereof, and in which:

Fig. 1 is a partial vertical sectional view illustra'ting more or less diagrammatically, a steam generator embodying the invention, and

Fig. 2 is an enlarged transverse vertical sectional view of the steam and Water drum shown in Fig. l.

Referring to the drawing, reference character It designates the setting of a steam generator comprising an upper or steam and Water drum II, and a main bank of steam generating tubes l2, which are vertically inclined and extend between headers !3 and I4 and a drum l5, and which are connected with the upper drum H by riser tubes [6 and downcomers l1. Groups of water wall tubes l8, l9 and 2!! also form a part of the steam generating surface and circulatory system of the unit. The lower portion of the combustion chamber 21, is lined by these water wall tubes, and it is provided with suitable fuel burning equipment, not shown, for producing products of combustion. in the. required volume and at the required temperature. Suspended from the upper portion of the setting and extending downwardly into the space between the tubes 16 and I I, is a superheater 22 having steam inlet and outlet headers 23 and 24 respectively. The inlet header 23 is connected to the steam and water drum by saturated steam' line; 25; Combustion gases, after flowing, over the superheater 22, enter outlet flue 26 andlfl'owthroughduct 21 to a waste heat boiler section 28 and a non-steaming economizer 29, which are housed within casing structure 33. of the invention shown, the gases after leaving the economizer, enter an air heater 3| which includes the necessary air ducts, not-shown, for conducting preheated air to the fuel burning apparatus in the lower portion of the'combustion chamber, while-the spent flue gases aredischarged to the atmosphere-by a stack or other means, also not shown. Thesi'ze of the waste heat boiler section-is-determined by the quantity of heat of the flue gaseswhichit is economically desirable to absorbover and above the; heat absorbed by the economizer and the air heater, and also by the fact that the waste heat boiler section should have aheat absorbing surface sufliciently large to prevent steaming in the economizer section 29.

The steam drum H is provided with-a steam washer 32'and steam drying apparatus-53.- Any suitable type of thesteam washer may be-utilizedz The type shown includes a tray 34 which is-disposed horizontally above the water level inthe drum and is provided with aplurality of-parallel; elongated upwardly extending nozzle=like steam ports 35, Extending over the topof each of these ports and slightly spaced therefrom, is a cap member 35 the lower edges of'the sides of which are cut away as indicatedat' 31'.

In operation, feed water from the economizer 29 is supplied tothe tray 34 of' the washer by feed, line 38; This water flows across thetray between the ports-35to an outlet pipe 39'; which has itsupper end disposed to maintain the desiredwater level on thetray. The pipe 39 conducts the overflow from the-tray 34 to the boiler circulating water in the lower portion of-' the drum. Steam liberated in thespace below the washer passes upwardlythe-ports in theiray; is deflectedby the cap members3B'and'flowsd0wnwardly through the water on the tray and under the lower edges of the sides of the capmembers, and then upwardly through thewashing water which frees the steam substantially of its solidcontent. Afterpassing through the-Wash water, the washed steam flows through thedrier 33 to the steam line 25' and thence to the superheater.

Feed water from any suitable source is' forced by pump 40 through line 4| to the economizer inlet header 42, and through the economizer tubes to outlet header 43'. Theeconomi'zerheating surface'will-be proportioned so that the water at the outlet header will have almost reached the saturation temperature'of the water at the pressure existing in the boiler drum.- This water, which isfree ofsteam iSthen conducted by feed line 38 directly tothesteam washer inthe drum as previously explained.

In the embodiment Water from the bottom of the drum H is supplied to the waste heat boiler section 28 through a plurality of connecting tubes 44, intermediate header 45, feed line 44', and inlet header 46. A mixture of steam and water is discharged from the waste heat boiler section. intov outlet header 4! and i conducted to the drum H through line 48.

From the foregoing it will be perceived that the invention provides a simple and efiective means and method for obtaining the advantages from a heat. recovery standpoint of steaming economizers andlat: the same time entirely avoiding. the aforesaid. difficulties in connection with their use-whichheretofore have had to be overcome by more costly and complicated means,

Inasmuch as changes may be made in the specific form,- location and arrangement of the several: parts of thhe invention disclosed without departing from the principles of the invention, it will be-understood that the invention is not to'be-limited excepting by the scope-of the appendedclaims.

What is claimed' is:

1-: A vapor generator comprising a-Vaporgenerating section, avapor and liquid' drum connected withsaid section, a vapor andtliquidcontact device in the drum, a gas passagearranged toreceive gases after having passed inheat exchange relationship with said section, an economizer'inrthe'gas passage, additional vapor generating' surface disposedin saidpassage so that the-gases flow; in contact therewith prior' to flowing into heat exchange relationship with the economizer, a conduit-connecting the outlet of the-economizer' with the vapor and liquid contact device; and additional conduitsconnectingthe inl'etand outlet of said additional-surface to' said drum, said additional conduits being: out: of heat exchange relationship with said gases, said'additional surface beingconnected to said drum in parallel with said vapor generating section and having: a heat absorbing surface area sufliciently large to prevent vaporization in the: economizer thereby. to prevent delivery of 'vapor. to said vapor and liquid" contact device.

2;. Tlrie=method of generating. vapor in. a. generator havinga vapor?generatingsection, avapor and: liquid drumi connected to the section and a vapor and liquid contact d'evic'e inathe drum, which comprises-heating.-liquid for the generator by the gases flowing from: heat exchange: relae tionship: with the vapor generating. section, delivering the. heated liquid to said device in the drum, andcirculatingJfiuid toand' from the drum in heat exchange: relationship with the gases prior to theirr'flow into hcatingrelationship.with said liquid; to cool the gasesisufficiently to prevent vaporizationv of the heatedliquiddelivered to saididevice:

3-. The method of generatingisteam. in a generator having a steam generating section, a steam and water drum connected to :saidisection andl av steam washer inflthe drum, which. comprises heating water for the generator by the gases: flowing: from heat exchange relationship with. the steam generating section, delivering the heated water to the steam washer, and; circulating water naturally to and'ffrom the drum in heat exchange relationship with the gases prior to. their: fiowinto he'atingrelationship with the water delivered to the washer to cool the gases sufiiciently to prevent steaming of the water deliveredto'the washer. V

WALTER F. KEENAN,.JR.

CERTIFICATE OF CORRECTION. Patent No. 90,88 July 28, 19L 2.

WALTER F. KEENAN, JR.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page first column, line 55, after the word "upwardly" insert --through and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 25th day of August, A. D. 19h

Henry Van Arsdale,

(Seal) Acting Commissioner of Patents. 

